<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>计算字符串中某字符出现的次数</title>
    <script>
        var str = '21352572346265247';
        var index = str.indexOf('2')
        var num = 0
        while (index !== -1) {
            console.log(index);
            num ++;
            index = str.indexOf('2',index + 1)
        }
        console.log('2出现的次数为：' + num + '次');
    </script>
</head>
<body>
    
</body>
</html>